1. Field
This embodiment relates to a signal transmission apparatus which performs transmission of a signal via a transmission line and a signal transmission apparatus control method.
2. Description of the Related Art
Devices using the PCI (Peripheral Component Interconnect) standard and the PCI-X standards, which have been used for personal computers and servers have been transitioning to the PCI Express standard. ATA (Advanced Technology Attachment), which has been used for connection of a storage device such as a hard disk and a CD-ROM, has been transitioning to Serial ATA. Similarly, SCSI (Small Computer System Interface) has been transitioning to Serial Attached SCSI.
Thus, the electrical interface for signal transmission rapidly transitions from a parallel interface to a serial interface.
Since the serial interface uses a wider band than the parallel interface, there is a demand for a method for appropriately determining loss, jitter, noise, variation and the like in a transmission line, and also for obtaining a more stable transmission waveform.
The serial interface has a transmission LSI (Large Scale Integration) device for sending out a signal waveform; a transmission line configured by a printed circuit board, a connector and a cable; and a receiving LSI device for receiving a signal waveform.
Designing a high-speed transmission system with a GHz-order transmission speed is required to obtain an optimum transmission quality requires consideration of the capability of a transmitter and a receiver, variation of characteristics of elements and substrate materials, characteristics of each of elements constituting a transmission line, noise and the like.
A conventional transmission system has a printed circuit board, a cable and a connector in addition to the transmission LSI device and the receiving LSI device. Examples of items to be considered in this case include: transmission and receiving performance; variation of LSI's, materials and characteristics; power source and crosstalk noise; reflection; loss of PCB (Printed Circuit Board) wire, VIA, cable, connector and transmission/receiving LSI package; and the like.
In the related art, there are an equalizer for automating setting of an equalization parameter and a pre-emphasis adjustment method for shortening the time required for pre-emphasis adjustment (see Japanese Laid-open Patent Publication No. 2004-015622 and Japanese Laid-open Patent Publication No. 2006-246191, for example).
In general high-speed transmission, receiving eye opening adjustment and EQ (equalizer) adjustment by the emphasis adjustment are performed. However, since the transmission clock frequency is specified in advance, an optimum transmission method is not necessarily realized.
Recently, a high-speed transmission system is provided with a plurality ports, and a multi-port transmission/receiving circuit is included in an LSI device. Therefore, it is feared that the transmission quality may be deteriorated by open reflection in an open lane or noise by simultaneous operation of multiple lanes. Furthermore, though it is often assumed that the receiving margin is increased by increasing the receiving eye opening, noise inside the multi-port LSI is increased by receiving a large eye opening waveform. Similarly, deterioration of the transmission quality may be also caused.